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|United States Patent
September 1, 1992
Load lift truck
A load lift truck having a vertically extendible mast adapted for
longitudinal displacement along a length of the truck chassis is
disclosed. The truck includes a carriage mounted on the mast adapted for
lateral displacement along the mast. The carriage fitted with a
load-carrying fork arrangement is adapted for angular rotation about a
vertical axis. The truck is adapted for simultaneous operation of each of
the aforesaid displacements and rotation thereby providing a means of
maneuvering a load within a markedly smaller spatial environment with
Harper; Clark N. (8814 Oak Valley Dr., Sandy, UT 84093)
May 6, 1991|
|Current U.S. Class:
||414/629; 187/229; 414/631 |
|Field of Search:
187/9 R,9 E,95
U.S. Patent Documents
|3907141||Sep., 1975||Ahrendt et al.||187/9.
|Foreign Patent Documents|
Primary Examiner: Olszewski; Robert P.
Assistant Examiner: Noland; Kenneth
Attorney, Agent or Firm: Trask, Britt & Rossa
Parent Case Text
This is a continuation of application Ser. No. 312,119 filed Feb. 17, 1989
now U.S. Pat. No. 5,036,952.
What is claimed is:
1. A lift truck comprising:
a chassis supported by a ground engaging means;
a load carrying carriage mechanically associated with said chassis;
a first displacement means mechanically associated with said carriage for
displacing said carriage longitudinally along said chassis;
a second displacement means mechanically associated with said carriage for
displacing said carriage laterally along said chassis; and
a third displacement means, mechanically associated with said carriage for
angularly rotating said carriage about said chassis;
wherein said first, second and third displacement means are simultaneously
operable to maneuver a load carried by said carriage to a selected
location and orientation.
2. The lift truck of claim 1 wherein said first driving means is a
pressurized fluid cylinder.
3. The lift truck of claim 6 wherein said pressurized fluid cylinder is a
4. The lift truck of claim 1 wherein said first driving means is an
5. The lift truck of claim 1 wherein said second drive means including a
6. The lift truck of claim 1 wherein said second drive means is formed by a
pair of hydraulic motors each motor having a toothed gear mounted on a
respective drive shaft thereof, said motors being mechanically associated
by an endless chain trained over said gears.
7. The lift truck of claim 1 wherein said carriage includes a plurality of
third pressurized fluid cylinders mounted thereon and forks pivotedly
mounted to said carriage, said third cylinders being mounted to said forks
to effect a tilting of said forks.
8. A lift truck comprising:
a chassis supported by wheels, said chassis having at least one outwardly
extending outrigger mounted thereon, said outrigger being supported by a
ground engagement means, said outrigger defining a first guide track;
a mast mounted on said outrigger guide track to be displaceable along a
length of said first guide track;
first driving means mounted on said mast for reciprocably displacing said
mast longitudinally along said guide track;
a support, having a second guide track, mounted on said mast;
an extension mounted on said second guide track for lateral reciprocal
displacement along said second guide track;
a second drive means mounted on said support for displacing said extension
along said second guide track; and
a carriage pivotably mounted on said extension for rotation about a
vertical axis, said extension including a third drive means adapted for
angularly rotating said carriage about its axis relative to said
extension, said carriage including a load-carrying fork means mounted
wherein said first, second and third driving means are operable
simultaneously to maneuver said fork means to a selected location and
9. The lift truck according to claim 8 wherein said fork assembly includes
a tilting means for tilting and inclining said assembly from a horizontal
10. The lift truck of claim 8 wherein said second guide track is defined by
a dual-directional pressurized fluid cylinder.
11. The lift truck of claim 8 wherein said load carrying carriage includes
mast constructed to be vertically extendible and retractable, said mast
including a fourth drive means mechanically associated therewith for
drivingly extending and retracting said mast.
BACKGROUND OF THE INVENTION
This invention relates to load carrying apparatus. More particularly, this
invention is directed to load lifting trucks.
2. State of the Art
Modern day storage facilities place a premium value on the use of physical
space within such facilities. In order to optimize the use of space, such
facilities are conventionally organized to include a plurality of rows of
pallet racking on which articles are stored. Each pair of rows is
separated by an aisleway dimensioned to permit a warehouseman to pass
therethrough in order to access articles located in one or the other of
the opposing rows of pallet racking. It follows that economy dictates that
space within a warehouse should be allocated firstly to actual storage,
with space allocated to aisleways being minimized to onlly that required
for actual passage of a lift truck.
Lift trucks of various configurations are known in the art. Conventionally,
trucks include an extendible mast having a pair of outwardly extending
forks mounted thereon adapted to engage, lift and otherwise convey an
article to be transported. Recently, efforts have been made to modify the
function of the mast to achieve enhanced operational capabilities. For
example, in one type of lift truck, known as a rolling mast reach truck,
the mast has been made longitudinally displaceable along the length of the
truck. In other configurations, the forks have been displaceably mounted
for movement laterally across the face of the mast. Each of these various
mast constructions include advantages as well as disadvantages, owing to
their particular operation and structure.
A conventional rolling mast-type reach truck is shown in FIGS. 1-6,
positioned within a aisleway of a storage facility. Observably, the
figures are not drawn to scale. The aisleway is dimensioned to have a
width considerably in excess of the width of the truck, due to the
necessity of providing space for the truck to maneuver into a position
where it can engage, load and retract an article to be transported. In
order to properly load an article onto the truck, the truck must be
aligned squarely with the article. The path of a truck preparing to load
an article is shown by a dotted line in FIG. 1. As shown, the truck
travels longitudinally down the aisleway. It begins to turn to the left
until it aligns itself squarely with the article to be loaded. Observably,
this maneuver requires the aisleway to have a width (A) which is not only
broader than the width (B) of the truck, but furthermore, the width (A)
must be dimensionally longer than the length (C) of the truck. The width
(A) must be sufficiently large to permit the truck to back up from its
abutment or loading and maneuver into a position whereby the operator can
drive the truck longitudinally down the aisleway.
Upon the truck reaching the condition shown in FIG. 3, the mast (D) of the
truck is extended longitudinally from the truck (as shown by the arrows),
thereby urging the forks under the article to be loaded.
Thereafter, the mast (D) of the truck is raised sufficiently to elevate the
forks and thereby raise the article and effectively load it on the forks
(FIG. 4). Thereafter, the mast is retracted toward the truck chassis (E),
as shown by the arrows, bringing the loaded article with it. As shown in
FIG. 4, the article and mast are retracted to a position proximate the
truck chassis. Subsequently, the truck must re-execute the aforedescribed
maneuver in reverse in order to bring the truck into an orientation which
permits its travel down the aisleway.
As shown in FIG. 5, oftentimes the dimensions of the articles to be
transported measurably increase the effective length of the lift truck
after the article is loaded on the truck's forks. See length indicated
generally as (F). Naturally, this increase in length due to the
contribution of the article must be accounted for in determining the
required width (A) of the aisleway. Often-times, the combined length of
the truck in association with its loaded article dictate the dimensioning
of an aisleway which is exceedingly wide.
One of the most critical aspects of a lift truck is its load carrying
capacity. This capacity is in large part predicated on the particular
geometry and function of the truck itself. For example, the truck shown in
FIGS. 1-6 includes a pair of outriggers (H) which extend outwardly
parallel one another longitudinally from the truck. Each outrigger engages
the ground by means of a wheel mounted proximate the free end of the
outrigger. When unloaded, the truck's center of gravity, identified
generally by the notation (CG) is located proximate the main truck chassis
as shown in FIGS. 1-6. As the forks are extended, that center of gravity
is displaced longitudinally along the truck's length. When the truck
actually lifts the article to be transported, the truck's center of
gravity shifts dramatically toward the front of the truck as shown by the
notation (CGT) in FIG. 4. If the center of gravity (CGT) shifts
longitudinally beyond the point of the engagement of the outrigger wheels
with the ground, indicated by plane identified by the dotted line (I), the
truck is longitudinally unstable and will tip toward the loaded article
and may eventually turn over. As a result, for a chassis having a given
weight, the load carrying capacity of the truck is dependent on
maintaining the (CGT) on the vehicle's side of the plane indicated by the
dotted line (I) in FIG. 4.
Noticeably, the drawback of the conventional rolling mast truck is its
requirement of relatively wide aisleways suited to permit the type of
truck maneuvering necessary to orient the truck for loading and unloading
an article to be transported. As previously discussed, the allocation of
space for aisleways in storage facilities should preferably be minimized,
since space allocated for aisleways reduces the quantity of space which
may be used for storage. This follows, as a recognition that storage
space, not aisleway space, is regarded as the prime and foremost priority
in storage facilities.
FIGS. 8-10 illustrate the loading maneuvers of a conventional lateral
turret lift truck. As shown in FIG. 8, a truck of this construction
includes a pair of loading forks (J) which are oriented transverse of the
longitudinal axis of the vehicle. The forks are mounted to a carriage and
pivot head (K) which is constructed to be laterally displaceable along a
structure (L) positioned on the front of the truck. The forks are made
rotatable about the support, thereby permitting the forks to retrieve and
load articles from either side of the vehicle. For example, the vehicle
illustrated in FIGS. 8-10 is shown loading from the left side of the
aisle, the truck could equally well load from the right side.
As shown in FIG. 8-10, the truck is driven to a location proximate the
article to be loaded and the forks (J) are aligned in register with the
article. A lateral translation of the forks across the face of the truck
urges the forks beneath the article (FIG. 9). A lateral reversal of the
forks and its supporting carriage causes the article to be retracted
.outwardly from its storage location in a direction generally
perpendicular to the longitudinal axis (M) of the aisleway. Noticeably,
the width (A) of the aisleway is determined by the length (N) of the
article in combination with the depth of the fork carriage and the
associated pivot head (P).
As shown in FIG. 12, the turret truck may pivot the fork carriage so as to
orient the article transported collinearly with the longitudinal axis of
the truck. In doing so, the operator must typically retract the article
completely out of the shelf location before initiating any pivoting
motion. When the article is carried in this forward facing orientation,
the moment created by the article transported on the truck is maximized
due to the length of the effective moment arm (R.sub.2).
There continues to be a need for a truck which requires a minimal quantity
of aisle space for maneuvering during its loading and unloading
operations. Further, there continues to be a need for a truck whose
operation maximizes its load carrying capability.
SUMMARY OF THE INVENTION
The lift truck of the instant invention includes a chassis supported by one
or more of ground engaging means, e.g., power driven wheels. The chassis
includes at least one outwardly extending outrigger-type support which is
supported above the ground on its free end by a wheel or other support
means, e.g. a sled.
In a first embodiment, the outrigger support defines a guide track therein
adapted for guiding an upright mast longitudinally along a length of that
track. The mast, which may be of a vertically telescopically-extendible
type, is mounted within the track by rolling means which permit a minimal
drag translation of that mast along the track. A first drive means which
may be a pressurized fluid cylinder, e.g., a hydraulic or pneumatic type,
is mounted to the truck chassis and the mast. The first driving means is
adapted for displacing the mast longitudinally along the chassis. The
first drive means is dual-directionally-actuatable, thereby permitting an
operator to drive the mast in either a forward or backward motion along
The mast, if it is of an extendible type, includes a second drive means,
e.g., a pressurized fluid cylinder adapted for drivingly extending and
retracting the mast. Such means may include a pressurized fluid cylinder,
a chain drive connected to an actuating motor which may be of an electric,
gas, diesel, or liquid propane gas-type. Alternatively, any other means
capable of translating the extension along the face of the support may be
used. Fixedly mounted on the free end of that mast is a laterally
extending support fitted with an outwardly extending arm. The support
defines a guide track therein adapted for guiding the arm's lateral
translation along the face of the support. The support includes a third
drive means adapted for forcedly driving or shifting the arm laterally
along the support. In preferred embodiments, the shifting means may
include a dual-directioned pressure fluid cylinder which itself defines
the guide track.
The arm is mounted on its outermost free end with a pivotedly mounted
carriage having a plurality of outwardly extending load-carrying forks
mounted thereon. The support may include a fourth drive means adapted for
rotating the carriage, e.g., about a vertical axis. The third drive means
may include a hydraulic motor, electric motor, pressurized fluid cylinder
or other conventional system as its power generating means.
The forks on the carriage may include one or more powered tilting means
attached thereto adapted for tilting the forks by applying a preselected
directioned force application to those forks.
In operation, the association of the longitudinally displaceable mast,
laterally translatable arm and rotationally mounted fork fitted carriage
provides the operator with a means of transporting a load down an aisleway
which is dimensioned to closely correspond with the width of the load. The
first, second, third, and fourth drive means are adapted to be
independently operated or alternatively, operated in conjunction one with
another. Indeed, all four of the drive means can be operated
simultaneously to yield a displacement of the load along a selected path.
This capability to direct the load along a selected path provides two
critical benefits to the invention. First, the operator is able to
retrieve and deposit loads from or onto aisle shelf locations, utilizing a
measurably smaller aisle space for maneuvering purposes. More
specifically, the invention provides a lift truck having maneuvering
capability utilizing four-degrees of freedom. The association of multiple
drive means allows the operator a four-way means of maneuvering the load
during retraction and deposition. An operator of the invention can
simultaneously displace the load longitudinally (either forward or away
from the truck chassis), laterally and vertically and may further pivot
the load about a vertical axis.
A utilization of all of these functions simultaneously, i.e., longitudinal
displacement, lateral displacement pivoting and vertical displacement,
provides the user with the capability to maneuver a load about a
90.degree. angle while maintaining tight control over the location of the
center of gravity of the load. This control permits the operator to shift
the load from a forwardly facing load orientation to an orientation which
is ninety degrees removed therefrom while maintaining the longitudinal and
lateral stability of the loaded truck. The invention permits that shifting
to be either to the left or the right. The configuration of the truck
permits the operator to retain the center of gravity of the load during
the unloading and loading maneuver, closer to the chassis, thereby
minimizing the length of the movement arm of the load's center of gravity
and as a result, maximizing the load carrying capability of the truck
while optimizing stability. Further, this maneuvering capability permits
an operation to optimize utilization of the geometry of the shelf space so
as to minimize the amount of aisle space required for loading,
transporting and unloading an article. The fork carriage of the invention
may also be fitted with a tilting means adapted for tilting the carriage
forks, thereby increasing the stability of an article loaded on those
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top plan view of a prior art rolling mast lift truck shown in
an aisleway, preparing to engage a load to be lifted.
FIG. 2 is a top plan view of the lift truck of FIG. 1, reorienting itself
to align its lift forks to register with the load.
FIG. 3 is a top plan view of the lift truck of FIG. 3 having its forks in
register with the load.
FIG. 4 is a top plan view of the lift truck of FIG. 1 having its forks
extended beneath the load.
FIG. 5 is a top plan view of the lift truck of FIG. 1 showing the truck
retrieving the load from its shelved location.
FIG. 6 is a top plan view of the lift truck of FIG. 1 showing the truck
reorienting itself in the aisle to permit its travel along the length of
FIG. 7 is a side view of the truck of FIG. 1.
FIG. 8 is a top plan view of a prior art lateral lifting truck positioned
in an aisleway.
FIG. 9 is a top plan view of the truck of FIG. 8 showing its lifting forks
being inserted beneath a shelved load to be lifted.
FIG. 10 is a top plan view of the truck of FIG. 8 showing the load being
retracted perpendicularly from its shelf location and positioned for
travel longitudinally down the aisleway.
FIG. 11 is an end view of the truck of FIG. 8.
FIG. 12 is a top view of respectively a turret truck, a truck of the
invention and a rolling mast reach truck.
FIG. 13 is a perspective view of a preferred embodiment of the lift truck
of the invention showing the lifting forks in an outwardly extending and
the elevated orientation with the mast fully extended and the turret
attachment fully extended.
FIG. 14 is a perspective sectional view of the fork-fitted mast of the lift
truck of FIG. 13.
FIG. 15 is a perspective view of the lifting forks and separate carriage of
a lift truck of the invention. .
FIG. 16 is a perspective view of a second embodiment of the lift truck.
FIG. 17 is a side view of the lift truck shown in FIG. 16 with the mast in
the retracted position.
FIG. 18 is a rear view of the lift truck shown in FIG. 16 with the mast and
lifting forks removed.
FIG. 19 is a perspective sectional view of the rolling mast of the lift
truck of FIG. 16.
FIG. 20 is a perspective sectional view of the forks and support carriage
of the lift truck of FIG. 16.
FIG. 21 is a side view of the forks and support carriage of the lift of
FIG. 22 is a top plan view of the lift truck of the invention-having the
mast extended and the forks rotated to the side and laterally extended.
FIG. 23 is a top plan view of the lift truck of the invention with the
forks oriented forward and positioned proximate the truck chassis.
FIG. 24 is a top plan view of the truck of FIG. 23 showing the forks and
support carriage being rotated counterclockwise. The carriage is also
depicted as being laterally shifted. The mast is shown being extended
forward (longitudinally). The aforesaid rotation, shifting and extension
are indicated pictorially by arrows on the FIG.
FIG. 25 is a top plan view of the lift truck of FIG. 24 showing an
advancement of the longitudinal extension or displacement of the mast
(indicated by arrow) in association with the further advancement of the
counterclockwise angular rotation (as shown by an arrow). The forks have
been rotated to face approximately ninety (90) degrees from the
orientation shown in FIG. 23. The carriage is also shown being displaced
to the left (as indicated by an arrow).
FIG. 26 is a top plan view of the lift truck of FIG. 23 showing the forks
being further shifted laterally from an orientation ninety degrees
(90.degree.) removed from the position shown in FIG. 23, bringing the
forks into position beneath a shelved load to be lifted.
FIG. 27 is a top plan view of the lift truck of FIG. 23 showing the
carriage being shifted laterally to the right (indicated by an arrow). The
figure further illustrates a clockwise rotation of the carriage, as
indicated by an arrow. The mast is also depicted, by an arrow, as being
retracted toward the truck carriage.
FIG. 28 is a top plan view of the lift truck of FIG. 23 showing a clockwise
rotation of the carriage, shown by an arrow. A retraction of the mast
toward the truck chassis is illustrated by the arrow. The lateral
displacement of the carriage to the left is also shown.
FIG. 29 is a top plan view of the lift truck of FIG. 28 showing an
advancement of the combined rotation and longitudinal displacement shown
initiated in FIG. 28.
FIG. 30 is a top plan view of the lift truck of FIG. 23 showing the forks
and load in an orientation suited for transport.
FIG. 31 is a top plan view of the lift truck of FIG. 23 showing a plurality
of fork and carriage orientations through which the fork and carriage pass
during a typical loading operation.
FIG. 32 is a perspective view of a third embodiment of the invention.
FIG. 33 is a sectional view of the embodiment illustrated in FIG. 32.
FIG. 34 is a top view of the truck of the invention illustrating the path
of the load's center of gravity during the loading operation.
DETAILED DESCRIPTION OF THE INVENTION
The lift truck of the invention is illustrated in FIG. 13. The truck,
generally 30, includes a chassis 32 which is supported by a plurality of
wheels 34. While a three-wheel embodiment of the invention is illustrated,
it should be understood that four-wheel constructions are also
contemplated. The chassis 32 includes a box-like housing 36 which encloses
the drive unit of the truck, which may be either an electric motor or an
internal combustion engine. The truck includes a drive train which
intercooperates the drive unit with one or more of the truck wheels 34.
Various cooperation schemes for linking the drive unit to one or more
drive wheels is contemplated. For example, the front wheels may be driven,
alternatively the rear wheels may be driven.
A seat 38 for the truck's driver is mounted atop housing 36, the steering
wheel 40 and other controls are mounted on a console positioned proximate
seat 38. While a seat 38 is provided, it should be understood that the
instant invention could also be configured in a stand-up embodiment,
wherein the operator stands instead of sits. A protective cage-like
structure 42 extends upwardly from the housing 36 to form a rigid
protective structure about a driver seated on seat 38.
Extending longitudinally from chassis 32 is a pair of elongate
outrigger-like supports 44 which are shown more clearly in FIG. 14. The
supports 44 are each formed of a structural member, e.g., a "U"-shaped,
channel-defining stock. As illustrated in FIG. 14, each support 44 is
oriented such that the open side of the support is oriented vertically to
face the vertically-oriented open side of the opposing support 44. Each
support 44 is a linear member. The interior of each support defines an
elongate linear channel 45 which functions as a track for one or more
wheels or rollers 46 mounted therein. The supports 44 are oriented
parallel one another to define a track which extends longitudinally from
the truck housing 36.
Each of the rollers 46 is journaled on a respective axle 52 which is
fixedly mounted as a horizontally positioned mounting bracket 54. In FIG.
14, the roller 47 and mounting bracket 54 have been removed from the
left-hand channel support 44A for clarity purposes. It should be
understood, however, that the left-hand support is a mirror reflection of
the right-hand support configuration. The bracket 54 is longitudinally
displaceable along the length of supports 44 in either a forward and
backward direction by the action of one or more pressurized fluid,
rod-fitted cylinders 56. Recognizably, other drive configurations could be
adapted, e.g. motor driven chain arrangement, a worm gear construction or
alternatively, a rodless cylinder arrangement. The cylinders 56 may be of
a hydraulic or pneumatic-type construction, and are each adapted for dual
directional action, i.e., each cylinder is configured to apply both a
pushing force as well as a pulling force on the bracket 54, with the
particular direction at any one moment being determinable by the operator.
The bracket 54 is therefore adapted for travel in the directions indicated
by arrows 55A and 55B. The cylinders 56 are each mounted to a cross-brace
58 which interconnects the two brackets 54 and forms part of the bracket
As shown in FIG. 14, outrigger supports 44 include a pair of wheels 34A
mounted thereon. Each wheel 34A is journaled on an axle 60 which is
fixedly mounted to a respective support 44 proximate the free end thereof.
The use of the wheels 34A provide a two-point support means for each
support 44 and 46, i.e., the support mounting on chassis 32 and its
mounting to wheel 34A.
Mounted to the upwardly extending sections of bracket 54 is a three segment
mast arrangement 64 adapted for extension and telescopic or nesting
retraction. Understandably, other mast constructions may be utilized. For
example, masts of a single, double, quadruple or other multiple of
extendible segments may likewise be employed. As shown in FIG. 14, the
mast 64 includes a first pair of elongate, vertically upright,
parallelly-positioned first extensions 66 which are spaced positioned
apart from one another. Each extension 66 is fixedly mounted to bracket 54
proximate a respective end thereof to extend upwardly from that bracket
54. As shown, each first extension 66 is formed of a structural member,
e.g., "U"-shaped channel stock. A cross-brace 68 is mounted to each of the
first extensions 66 proximate the free ends thereof to extend
therebetween. The cross-brace 68 operates to give a degree of integrity to
the first extension arrangement.
A pair of elongate second extensions 70 are positioned spacedly apart
vertically upright and parallel one another in a nesting or telescopic
arrangement with the first extensions 66. As illustrated in FIG. 14, each
extension 70 is formed of a structural member, e.g. "I"-beam type member.
A flange of each "I"-beam contiguous extension 70 is received within a
respective, vertically-oriented channel defined by a respective first
extension 66. In this arrangement the second extension 70 is permitted
upward as well as downward displacement along the first extension 66. As
shown, a flange 72 of the first extension 66 likewise extends into an open
channel 64 which extends vertically along the length of second extension
70. Spacers are positioned within the channels of each extension 66 and 70
to retain the two extensions fixed against displacement vis-a-vis each
other in the directions indicated by arrows 55A and 55B. The extensions 66
and 70 are freely mounted vis-a-vis each other to permit a vertical
extension of extension 70 vis-a-vis first extensions 66. A cross-brace 78
is mounted to each of the second extensions 70 to extend therebetween to
add structural integrity to the two extensions.
A third pair of extensions identified generally as third extensions 80 are
mounted in a nested or telescopic relationship with second extension 70.
As shown in FIG. 14, each third extension 80 is an elongate linear
structural member, e.g. a "I"-beam like member, having a flange thereof
positioned and aligned within an upright, elongate channel defined within
the structure of a respective second extension 70. This alignment operates
as a track to guide the respective third extension in its upward and
downward displacements relative to its respective proximate second
extension 70. The two third extensions 80 are positioned spacedly apart,
upright and parallel one another similarly to the previously described
first and second extensions 66 and 70.
A cross-brace 82 is mounted to each third extension to extend therebetween,
forming a bridge or linkage between the two third extensions, thereby
adding structural rigidity and integrity to the third extension
A fluid pressure actuated, two-segmented cylinder 84, of either the
pneumatic or hydraulic type, is mounted to cross-brace 58. Cylinder 84 is
oriented vertically upright. The free end of the cylinder rod 88 is
fixedly mounted to cross-brace 82 whereby upon an initial pressurization
of that cylinder 84, the third extensions 80 are elevated upwardly. The
cylinder 84 may be a dual-directioned cylinder. Alternatively, a two-,
three- or four-stage telescoping cylinder may be used.
Fixedly mounted to the free ends of the third extensions 80 is a laterally
extending support 90. As shown to advantage in FIG. 15, support 90 forms a
housing in which is mounted a horizontally oriented double-acting cylinder
92. The ends of the two rods 94 of the cylinder are fixedly mounted to the
support 90, the cylinder housing 96 is adapted for translation along the
length of the rods 94 in the directions indicated by arrows 98A and 98B
upon a pressurization of the cylinder. A collar 100 fixedly mounted on the
cylinder housing 96 is mounted with a hydraulic motor 102 having a
vertically oriented drive shaft 104, mounted with a horizontally oriented
toothed gear 106.
A support arm bracket 108 is mounted to the collar 100 and extends
outwardly therefrom. The arm bracket 108 is adapted for lateral
translation along a length of support 90 together with the cylinder 96. A
vertically oriented pivot shaft 110 is journaled in the free end of
support arm bracket 108. The shaft 110 is fixedly mounted at its ends to a
pair of spacedly positioned, horizontally and parallelly oriented,
carriage brackets 112. One bracket 112 is positioned above support bracket
108, the other, bracket 112 is positioned below that bracket, whereby
those brackets are free to rotate in a generally horizontal plane about an
axis defined by pivot shaft 110. Pivot shaft 110 is fitted on its end with
a toothed gear 114 around which is trained a pivot chain 116. Chain 116 is
also trained about gear 106 to form an endless, continuous configuration.
Carriage brackets 112 are each mounted to an upright carriage 120, which
is shown as a laterally extending box-like member. Pivotedly mounted to
carriage 120, proximate an upper region thereof, are two generally
"L"-shaped forks 122. The forks 122 are positioned spacedly apart from one
another in a generally parallel orientation.
A pressurized fluid cylinder 126 is pivotedly mounted to each respective
fork 122 proximate an angulated bend therein by means of a clevis-type
bracket 128 and a pivot pin 130 which passes through registered apertures
in that bracket and also through an eyelet-forming structure on the end of
the rod 132 of the cylinder 126. The cylinder housing section 134 of
pressure cylinder 126 is pivotally mounted to the carriage 120 by a
similar pivot fitting which, though not shown, is known in the art.
In operation, the lift truck 30 of the invention admits of four distinct
and separate means of displacing a load positioned on the forks 122.
First, the cylinders 56 permit the operator to displace the mast formed by
extensions 66, 70 and 80 in a forward and rearward longitudinal direction
relative to the chassis 32 of the truck. Cylinder 84 permits the operator
to raise or lower the mast vertically. Cylinder 92 operates to provide a
lateral displacement of carriage 120 across the face of the support 90.
Hydraulic motor 102 functions to permit a rotation of. carriage 120 about
a vertical axis 133. Tilt cylinders 126 may be utilized to tilt the forks
122 to retain the load in place.
An interaction of these four driving means permits the operator of the
truck to achieve a loading and unloading maneuver which not only requires
less operating space than prior existing trucks, but more importantly, the
displacement path of the load-bearing forks 122 relative to the truck
chassis is such that the displacement of the center of gravity of the
load/fork carriage assembly relative to the chassis, i.e. the moment arm
is constrained such that the moment arm length is considerably less than
the moment arms in conventional lift truck configurations. This results in
less of what is termed in the art as "lost load center." This particular
feature of the instant truck results in an increase in the load carrying
capability of the truck over conventional trucks, given a constant chassis
mass for each of the compared trucks.
FIGS. 16-21 illustrate an alternative embodiment of the invention wherein
the mast 57 is driven by one as opposed to two pressurized fluid cylinders
56. In this embodiment, the first, second and third mast extensions are
formed of a structural member, e.g. "U"-shaped members which are nested
one inside another. A respective pressurized fluid cylinder 84 is mounted
in association with each leg of the mast 57. In contradistinction to the
use of a dual-actioned cylinder 96 in support 90 as shown in FIG. 15, this
alternative embodiment of the invention includes two hydraulic motors 170
mounted upright in the support 90. Each motor 170 includes a toothed gear
172 fixedly mounted to each motor's drive shaft (see FIG. 20). An endless
continuous drive chain 174 is trained about the two gears to form a drive
track for the support arm bracket 108, which is fixedly mounted to that
chain along a portion of a length thereof.
In other respects, the construction of the alternative embodiment parallels
that of the embodiment described in the discussion of FIGS. 13-15.
FIG. 16 illustrates the use of a-pressurized fluid cylinder 176 adapted for
raising or lowering the support 90 relative to the mast 57. A more
detailed illustration of the linkage associating that cylinder 176 with
the carriage 120 is shown in FIG. 21. On each leg of mast 57 a chain 178
is fixedly mounted to the third extension 80 at its first end, and
thereafter trained over an annular pulley 175 journaled on the rod of
cylinder 176. The opposing end of the chain 178 is fixedly mounted to
support 90, a displacement of the rod of cylinder 176 causing a
corresponding displacement of the support 90.
For a better understanding of the features of the invention and the
intercooperation of the various driving means of the truck, resort is made
to FIGS. 22-23.
As shown in FIG. 23, the truck 30 of the invention may be effectively
operated in an aisleway which is only slightly larger than the width 136
of the truck. In contrast, the prior art devices, illustrated in FIGS.
1-10, require an aisleway having a width far in excess of the width of the
truck, as dictated by requirements for the trucks maneuvering to unload
and load articles to be transported.
As shown in FIG. 24, upon the truck reaching the location of an article to
be loaded, depending on whether the load is on the left hand or the right
hand of the truck, the support bracket 108 is shifted laterally across
support 90 while simultaneously the carriage 120 is rotated about pivot
shaft 110 by motor 102. Simultaneously, the mast is extended outward
longitudinally away from the truck chassis.
FIG. 25 shows the forks 122 being rotated into an aligned position in
registration with the article to be loaded. Observably, in FIG. 25, the
rolling mast arrangement of the truck has been extended to bring the
carriage 120 in full alignment with the article 137. Noticeably, the
chassis 32 of the truck has remained stationary during the entire
Subsequent to the alignment of the -carriage 120 as shown in FIG. 25, the
forks 122 are inserted beneath the article 137 by a translation of the
support bracket 108 across the face of support 90 by cylinder 92.
At this juncture, i.e. in the orientation shown in FIG. 26, the forks 122
are elevated by a vertical extension of mast 57, thereby lifting and
loading the article 137 onto the forks 122. In the condition shown in FIG.
27, cylinders 126 may be actuated to pivot forks 122 about their
horizontal axes 141, thereby tipping the article 137 into a more securely
loaded position by urging the article 137 against the vertical sections
143 of the forks 122.
Once the article is securely retained on forks 122, the support bracket 108
is displaced in the direction indicated by arrow 149 (FIG. 28) by the
action of cylinder 92. The end 151 of article 137 begins to approach the
front faces of adjacently positioned articles 153. The carriage is rotated
about axis 133 while simultaneously, the rolling mast 57 is retracted in
the direction indicated by arrow 153, bringing the mast 57 closer to the
truck chassis 32.
As the corner 157 of the article 137 clears the corner 159 of adjacent
article 161, support bracket 108 is translated in the direction of arrow
162 along the face of support 90, until reaching the central or midpoint
of support 90. Furthermore, the mast 57 is displaced toward the chassis
32. Simultaneously, the carriage continues its rotation about axis 133
until the article is brought into the forward facing orientation shown in
The truck effectively utilizes the spacing between adjacent shelved
articles for rotating the article to be transported and displacing it
toward the truck chassis during the loading process. This utilization
permits the operator to begin the rotation and displacement of the article
prior to the article having been completely removed from the shelf space.
This permits the operator to orient the article on the truck in a position
for its transport in a spatial area considerably smaller than that
required by either turret or rolling mast trucks.
FIG. 31 illustrates in a time-lapse format the path of the carriage 120
from its initial outwardly directed orientation to its ninety degree
rotation. The path of the circular carriage pivot during the reorientation
parallels the path of the center of gravity of the carriage during
loading. Whereas in contrast to the essentially linear translation of that
center of gravity, discussed in the description of the prior art lateral
shifting truck of FIGS. 8-9, the path of the center of gravity in the
inventive truck follows a generally "J"-shaped curvalinear path which
retains the center of gravity closer to the chassis during the loading and
FIG. 32 and 33 illustrate a second embodiment of the invention. In this
embodiment, a support 165 is mounted to be slidably displaceable along a
length of the outrigger supports 44. As shown in FIG. 30, the support 165
includes rotatably mounted wheels 167 mounted on the opposing ends
thereof, dimensioned to be received within a guide track formed by a
structural member, e.g. a "C"-shaped construction of each of the outrigger
supports 44. The support 165 is fitted with one or two dual-directioned
pressurized fluid cylinders 170, which are mounted on their first end to
the support 165 and at their opposing ends to the chassis 32. Being dual
directioned, the cylinders 170 are adapted to slide the support 165
longitudinally back and forth along a selected length of the outrigger
A dual-directioned pressurized fluid cylinder (e.g. a pneumatic cylinder)
172 is mounted horizontally on support 165. An outwardly protruding
extension 174 is mounted on cylinder 172. The cylinder 172 is adapted for
translating the extension 174 laterally across the face of support 165 in
a reciprocating motion. Extension 174 is fitted with a hydraulic motor 180
oriented upright such that its drive shaft is vertically oriented. A
toothed gear 182 is mounted on that drive shaft in a generally horizontal
A vertically extending mast 184 is pivotedly mounted to extension 174 by
means of a vertically oriented, elongate pivot pin 186. The mast 184 is
mounted to be angularly rotatable about a vertical axis 188. A toothed
gear 190 is mounted on pivot pin 186 in a generally horizontal
orientation. The gears 190 and 182 are mechanically intercooperated by
means of an endless drive chain 192 which is trained about the two gears.
The chain operates to translate an hydraulic motor-induced angular
rotation of the gear 182 to cause a corresponding rotation of mast 184.
In other respects, the construction of the mast 184, including its
extendibility function and the pressurized fluid cylinder adapted for
raising and lowering the mast, are similar structure-wise to the
aforedescribed mast structure 64. The carriage 120 may likewise be fitted
with one or more cylinders 176 adapted for fitting the forks 122, as
Operationally, this second embodiment in large part duplicates the various
movements previously described above appertaining to the first
The truck may also be fitted with a means of physically displacing a
portion of the chassis, mass, thereby modifying the moment of inertia
created by the chassis about either the longitudinal or lateral axis of
rotation. As shown in FIG. 32, a weight 194 is slidably mounted in a guide
track 196 mounted within the chassis 32 of the truck. The weight 194 is
displaced along the track 196 either toward or away from the chassis in
response to moments created on the truck by the imposition of loads on the
carrying forks 122. By adjusting the location of the weight 194, the
operator is able to effectively control the length of the moment arm of
that weight 194 and thereby adjust the magnitude of the moment created
thereby about the relevant rotational axis. Observably, the truck may be
fitted with more than one such weight. For example, one weight could be
oriented to be directed longitudinally from the truck while a second
weight is oriented for lateral displacement. Alternatively, a weight
having two degrees of freedom maneuverability could also be utilized. The
displacement of the weight 194 is controlled by a conventional linkage
which extends to a location proximate the operator's seat.
FIGS. 16 and 18 illustrate an alternative stabilizing means 195 wherein an
articulated stabilizing arm 197 is mounted to each of the sides of chassis
32. As shown, each arm is fitted with a pressurized fluid cylinder adapted
to engage the ground on either side of the chassis. Each arm 197 is
adapted to exert a reactive force on the chassis and thereby steady the
chassis by applying a lateral moment thereto.
Longitudinal stability is an essential characteristic of lift trucks. The
conventional reach truck is designed to ensure longitudinal stability by
controlling the location of a load's center of gravity (hereinafter "load
center") vis-a-vis an axis of rotation of the truck. In the truck
construction depicted in FIGS. 4 and 7, the truck's axis of rotation 200
during load retrieval is collinear with the axis of the truck's front
wheels. When a load is placed on the truck's forks, with the mast in its
most forward location (as occurs during initial retrieval of a load from
its shelf location), the load 201 creates a clockwise directed movement of
inertia 202 about the rotational axis 200 (see FIG. 7). The chassis
creates an opposing counterclockwise directed moment of inertia 204 about
the rotational axis which counteracts the moment generated by the load. As
long as the moment created by the chassis is larger than that created by
the load, the truck remains stable. If the load created moment becomes
larger than that created by the chassis, the truck overturns. The design
of the reach truck permits the user to physically move the load center
(CGL) toward the chassis by operating the rolling mast, preferably
positioning that load center on the chassis side of a vertical plane which
passes through the rotational axis, eliminating any load-created,
clockwise-directed moment about the rotational axis. In this preferred
orientation, the weight of both the load and the chassis is supported by
all of the wheels or supports of the truck, which condition contributes to
While the design of the reach truck contributes to enhancing a lift truck's
longitudinal stability, it simultaneously requires a relatively wide aisle
to facilitate the truck's maneuvering for its retrieval and unloading
operations. The reach truck must make a ninety degree (90.degree.) turn
within the width of the aisle during both retrieval and unloading. In the
truck's loaded condition, the total loaded length of the truck composed of
the actual length of the truck plus a portion of the length of the load,
is oriented within the aisle substantially perpendicular to the
longitudinal axis of that aisle. It follows that for the truck to maneuver
to a position whereby the truck can proceed longitudinally, i.e., a
90.degree. turn, the aisle must be dimensioned to be considerably wider
than the truck's loaded length. In conventional constructions, the length
of a lift truck is dimensionally larger than the truck's width.
Compared the reach truck, the particular design and operation of a turret
truck reduces the width of the aisle required for a truck's operation but
does not produce the longitudinal stability inherent in the reach truck
design. As shown in FIG. 11, a turret truck retrieves a load by the
lateral shifting of its load forks. As the truck initially lifts its load,
the load creates a moment of inertia 209 about a longitudinally extending
axis of rotation 210 which extends along the left or right side of the
truck, depending on which side the load is located. The moment is opposed
by a moment 211 created by the weight of the chassis about that axis 210
(see FIG. 11). Lateral stability is ensured provided the chassis created
moment exceeds the load created moment. After initially retrieving its
load, the turret truck displaces the load center toward the longitudinal
axis of the truck, thereby enhancing lateral stability. Upon the load
center's displacement through a vertical plane passing through the axis of
rotation, i.e. on the chassis side of the aforesaid plane, the load and
chassis are supported by all of the truck's wheels, thus achieving lateral
stability. The turret truck carries its load along the aisle with its
forks directed laterally as shown in FIG. 10.
The turret truck does not include means of enhancing the truck's
longitudinal stability. As shown, the load center is positioned on the
non-chassis side of a vertical plane passing through the front axle of the
truck. Resultingly, the load creates a counterclockwise directed moment
about an axis of rotation 213 oriented collinear with the front axle. The
turret truck has no means of eliminating this moment by moving the load
center through the vertical plane passing through the truck's front axle.
The turret truck's operation requires an aisle having a width which exceeds
the total length of the load (N) plus the dimension (P) of the pivot head
214 of the forks (see FIG. 10).
In contrast to the prior conventional lift truck configurations, the
instant invention provides a means of enhancing both the longitudinal and
lateral stability of a loaded truck while simultaneously reducing the
width of the aisle required for a lift truck's loading and unloading
As described, the new truck permits an operator to move the article's load
center subsequent to initial loading to a location on the chassis side of
both the lateral as well as the longitudinally extending axes of rotation,
thereby bringing that load center sufficiently proximate the longitudinal
axis 215 (FIG. 34) and lateral axis 216 of the truck so as to render the
truck longitudinally and laterally stable on its support wheels. Stated
otherwise, the load center is positionable by the lift truck with an area
outlined by the triangle or quadrilateral whose corners are defined by the
various ground engaging wheels of the truck. (See dotted line
representation in FIG. 24.) As a result, the instant invention provides a
means of advancing longitudinal as well as lateral stability by selected
displacement of the load.
Further, the inventive truck requires considerably less aisle width to
load, transport and unload an article than conventional trucks. As
illustrated, the instant truck due to its capability to simultaneously
utilize its four degrees of freedom maneuverability, can effectively
utilize the clearance between adjacent articles or rack members, space of
an open shelf during the initial phases of the unloading procedure,
thereby enabling the operator to complete either a retrieval or unloading
operation in an aisleway which is only slightly larger than the width of
the article to be transported.
To give some further meaning to these considerations, it is important to
consider that an average pallet supported load is generally 40" wide by
48" deep in dimension. A reach truck having a length of approximately 80"
typically requires an aisleway width of 7.5-8. ft. in order to properly
load, transport and unload the pallet supported load. The carriage
mechanism of a turret truck is typically approximately 56" wide, resulting
in the requirement of an aisleway of at least 66-68 inches in width in
order to ensure its proper operation. Should the operator want to unload
an article from one shelf and unload it onto a shelf on the other side of
the aisle, due to the turret truck's particular operation of carrying a
load in a side-facing orientation and the close tolerances between the
shelves on either side of the loaded truck, the turret truck operator must
actually exit the aisle before rotating the load 180.degree. to facilitate
the unloading of the load into the shelf facing the shelf from which the
load was retrieved unless the aisle is wider than 72 inches. Since few
warehouses are disposed to provide such additional end aisle space, the
conventional approach is to provide a truck for each aisle, i.e. an
aisle-captive truck. Alternatively, the load must be positioned at a
height and location which would allow rotation of a turret to extend into
openings to allow rotation within the confines of the aisle in a 68"
aisle. A turret truck cannot rotate a load from one side to another. Not
only is the operation time consuming but furthermore, the space required
at the end of the aisle to provide sufficient maneuverability of the
rotating forks is substantially in excess of that required for the
operation of other types of trucks having the ability to shift the
directions of a loaded article while the truck is within the aisle.
Further, the turret truck, in carrying the load such that its length is
oriented laterally, of necessity requires a turning radius which is
substantially in excess of the turning radius of the truck in which the
load is carried with its length oriented longitudinally. As a result,
while the design and operation of a turret truck may reduce the requisite
aisle width somewhat, that benefit is offset by the need for additional
space at the ends of each aisle. This additional space is required due to
the longer length chassis which a turret typically includes. In those
instances wherein the turret truck pivots the load for transport to a
forward facing orientation (see solid line representation of FIG. 12), the
truck suffers a loast load center of 24-28 inches.)
FIG. 12 permits a comparison of the longitudinal and lateral stability of a
turret truck 217, a truck of this invention 218 and a reach truck 219. For
each truck, the circles labeled CGL indicate the location of the center of
gravity of a load during the operation of unloading an article from a
shelf and into an orientation for transporting the load.
Regarding longitudinal stability with the turret truck, the load center
progresses along a laterally extending linear path 220 until reaching
approximately the edge of the chassis. At that point, the load is shifted
generally along a semicircular path to the orientation depicted as
CGL.sub.4. The location identified as CGL.sub.4 is the location in which
the load is retained during transport. Noticeably, the moment arm 224 of
the load's center of gravity remains essentially constant between the
locations identified as CGL.sub.1 through CGL.sub.3. Between CGL.sub.3 and
CGL.sub.4 the length of that movement arm increases markedly.
Understandably, any increase in that moment arm increases-the moment
created on the truck by the mass of the load. To determine the maximum
mass of the load that can be stably loaded by the truck, the maximum
moment arm length, i.e. R.sub.2 must be determined and utilized to compute
the maximum moment. Therefore, in the case of the reach truck, the load
carrying capability is determined by analyzing the moment created at
In the truck of the instant invention 218, the center of gravity of the
load progresses along a generally "J"-shaped path, the upright leg portion
of that "J"-shaped path being somewhat slanted. Noticeably, the moment arm
226 continuously decreases from a maximum length of location CGL.sub.1, to
a minimum length at CGL.sub.8. Resultingly, the maximum longitudinally
stable load carrying capability of the inventive truck is determined by
analyzing the moment created at CGL.sub.1.
In the case of the truck 219 the load-carrying capability is determined by
analyzing the moment at CGL.sub.1, i.e. moment arm 236.
Noticeably, the instant truck provides a construction having greater load
carrying capability in that due to the path of the load during the loading
and unloading operation, the longitudinal moment arm of the load is
minimized in comparison with the turret and rolling mast trucks.
Regarding lateral stability, the moment arms 233 and 235 of the respective
trucks 217 and 218 are substantiallly comparable, the reach truck 219
having generally little, if any, lateral stability problems.
The instant truck may be effectively operable in an aisleway having a width
of approximately 54 inches. Understandably, this width reduction of 25%
contributes to enhancing the quantity of warehouse space available for
storage. In addition, the invention provides a truck having greater
maneuverability and smaller or less- loss load center.
It may be noted that the embodiments illustrated herein are merely
illustrative of the application of the principles of the invention.
Reference herein to details is not intended to limit the scope of the
claims which themselves recite those features regarded is essential to the